The present invention is generally directed to power tools. In particular, the present invention is directed to a power tool having an actuation mechanism including an arrangement for preventing operation of the tool and also maintaining the tool in a continuous operating mode.
Conventional electrical devices frequently include an electrical switch for controlling the operation of the device. Examples of such electrical devices are disclosed in U.S. Pat. Nos. 2,420,585 to Crimmins, U.S. Pat. No. 3,378,662 to Sorenson, U.S. Pat. No. 4,095,071 to Chamberlain, and U.S. Pat. No. 4,454,785 to Pxc3xcrrer. Examples of electrical switches having a controlled movement include U.S. Pat. Nos. 3,249,725 to Hurt et al., U.S. Pat. No. 5,120,922 to Brouillette, and U.S. Pat. No. 5,813,522 to Lin.
Sorenson shows a typical power tool having an ON/OFF switch. This switch is controlled by a linkage including a trigger element, that is retracted into a body of the power tool against the action of a spring. The linkage further includes a plate having a row of serrations and a lock button. This lock button is biased by a spring out of engagement with the serrations. When the power tool is to be operated at a constant speed for extended periods of time, the trigger is retracted a desired distance and the lock button is depressed. This action causes the flange on the lock button to interengage one of the serrations, thus maintaining the trigger in the retracted position. Further retracting the trigger releases this interengagement and the lock button is moved out of engagement by the spring. Thus, the Sorenson linkage provides a consumer convenience feature for avoiding hand fatigue and for providing a mechanism that ensures the power tool can be continuously operated at a constant, predetermined speed for an extended period of time.
Another known arrangement providing the customer convenience feature of Sorenson is shown in FIG. 10. A power tool is shown to include an actuation mechanism including a trigger and a lock mechanism. In the illustrated position, lock out, the trigger is not able to be actuated. To actuate the trigger, the lock mechanism must be pushed to an intermediate position. Once, the trigger has been fully actuated, the lock mechanism may be pushed to a locking position, continuously engaging the trigger mechanism.
It is an object of the present invention is to provide a trigger mechanism including a locking device for blocking the movement of the trigger, thus preventing inadvertent operation of a power tool.
It is another object of the present invention to provide a trigger mechanism that is selectively positionable between a first mode blocking the movement of the trigger, a second mode allowing free manual movement of the trigger, and a third mode retaining the trigger in a position for continuous operation.
In one form, the present invention provides a power tool, a body, a trigger mechanism and a manually operated locking member. The trigger mechanism is mounted to the body for rotation about an axis between an actuated position and a non-actuated position. The manually operable locking member is translationally mounted to the body for movement between a first position and a second position. The locking member cooperates with the trigger mechanism to provide first, second and third modes of operation. In the first mode, the locking member is in the first position and articulation of the trigger mechanism from the non-actuated position to the actuated position is precluded. In the second mode, the locking member is in an intermediate position between the first and second positions and the trigger mechanism is freely allowed to articulate between the actuated and non-actuated positions. In the third mode, the locking member is in the second position and the trigger mechanism is prevented from articulating from the non-actuated position to the actuated position.
Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.